Improve hash combination

Per 4641ad2#r147400088

regression-tests/test-results/clang-12-c++20/pure2-hashable.cpp.execution

@@ -1 +1 @@
-10166087914140344613
+6440649391998984779

regression-tests/test-results/gcc-10-c++20/pure2-hashable.cpp.output

@@ -21,15 +21,15 @@ pure2-hashable.cpp2:1:7: note: candidates are: ‘constexpr base& base::operator
 pure2-hashable.cpp2:1:7: note:                 ‘constexpr base& base::operator=(const base&)’
 pure2-hashable.cpp2:6:14: note:                 ‘template<class auto:97> base& base::operator=(auto:97&&)’
 pure2-hashable.cpp2:1:7: note: ‘class base’ defined here
-pure2-hashable.cpp2:11:1: error: no declaration matches ‘mystruct::mystruct(auto:103&&, auto:104&&, auto:105&&) requires (is_convertible_v<typename std::remove_cv<typename std::remove_reference<decltype(mystruct::__ct ::i_)>::type>::type, const std::add_const_t&>) && (is_convertible_v<typename std::remove_cv<typename std::remove_reference<decltype(mystruct::__ct ::j_)>::type>::type, const std::__cxx11::add_const_t<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&>) && (is_convertible_v<typename std::remove_cv<typename std::remove_reference<decltype(mystruct::__ct ::k_)>::type>::type, const std::add_const_t&>)’
+pure2-hashable.cpp2:17:1: error: no declaration matches ‘mystruct::mystruct(auto:103&&, auto:104&&, auto:105&&) requires (is_convertible_v<typename std::remove_cv<typename std::remove_reference<decltype(mystruct::__ct ::i_)>::type>::type, const std::add_const_t&>) && (is_convertible_v<typename std::remove_cv<typename std::remove_reference<decltype(mystruct::__ct ::j_)>::type>::type, const std::__cxx11::add_const_t<std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > >&>) && (is_convertible_v<typename std::remove_cv<typename std::remove_reference<decltype(mystruct::__ct ::k_)>::type>::type, const std::add_const_t&>)’
 pure2-hashable.cpp2:5:7: note: candidates are: ‘mystruct::mystruct(mystruct&&)’
 pure2-hashable.cpp2:5:7: note:                 ‘mystruct::mystruct(const mystruct&)’
 pure2-hashable.cpp2:10:13: note:                 ‘template<class auto:98, class auto:99, class auto:100> mystruct::mystruct(auto:98&&, auto:99&&, auto:100&&)’
 pure2-hashable.cpp2:5:7: note: ‘class mystruct’ defined here
-pure2-hashable.cpp2:14:104: error: mixing declarations and function-definitions is forbidden
-pure2-hashable.cpp2:14:107: error: expected constructor, destructor, or type conversion before ‘{’ token
-pure2-hashable.cpp2:15:104: error: expected unqualified-id before ‘,’ token
-pure2-hashable.cpp2:15:107: error: expected constructor, destructor, or type conversion before ‘{’ token
-pure2-hashable.cpp2:16:104: error: expected unqualified-id before ‘,’ token
-pure2-hashable.cpp2:16:107: error: expected constructor, destructor, or type conversion before ‘{’ token
-pure2-hashable.cpp2:16:127: error: expected unqualified-id before ‘{’ token
+pure2-hashable.cpp2:20:104: error: mixing declarations and function-definitions is forbidden
+pure2-hashable.cpp2:20:107: error: expected constructor, destructor, or type conversion before ‘{’ token
+pure2-hashable.cpp2:21:104: error: expected unqualified-id before ‘,’ token
+pure2-hashable.cpp2:21:107: error: expected constructor, destructor, or type conversion before ‘{’ token
+pure2-hashable.cpp2:22:104: error: expected unqualified-id before ‘,’ token
+pure2-hashable.cpp2:22:107: error: expected constructor, destructor, or type conversion before ‘{’ token
+pure2-hashable.cpp2:22:127: error: expected unqualified-id before ‘{’ token

regression-tests/test-results/gcc-14-c++2b/pure2-hashable.cpp.execution

@@ -1 +1 @@
-10166087914140344613
+6440649391998984779

regression-tests/test-results/msvc-2022-c++latest/pure2-hashable.cpp.execution

@@ -1 +1 @@
-13273923326899311054
+13958440649017415620

regression-tests/test-results/pure2-hashable.cpp

@@ -57,14 +57,28 @@ auto base::operator=(auto&& h_) -> base&
 requires (std::is_convertible_v<CPP2_TYPEOF(h_), std::add_const_t<cpp2::i32>&>) {
                                                            h = CPP2_FORWARD(h_);
                                                            return *this;}
-[[nodiscard]] auto base::hash() const& -> size_t { return std::hash<cpp2::i32>()(h); }
+[[nodiscard]] auto base::hash() const& -> size_t{
+
+size_t ret {0}; 
+ret ^= std::hash<cpp2::i32>()(h) + (ret << 6) + (ret >> 2);
+return ret; 
+}
+
 mystruct::mystruct(auto&& i_, auto&& j_, auto&& k_)
 requires (std::is_convertible_v<CPP2_TYPEOF(i_), std::add_const_t<cpp2::i32>&> && std::is_convertible_v<CPP2_TYPEOF(j_), std::add_const_t<std::string>&> && std::is_convertible_v<CPP2_TYPEOF(k_), std::add_const_t<cpp2::u64>&>) 
                                                                                                        : base{ (1) }
                                                                                                        , i{ CPP2_FORWARD(i_) }
                                                                                                        , j{ CPP2_FORWARD(j_) }
                                                                                                        , k{ CPP2_FORWARD(k_) }{}
-[[nodiscard]] auto mystruct::hash() const& -> size_t { return base::hash() ^ (std::hash<cpp2::i32>()(i) << 1) ^ (std::hash<std::string>()(j) << 2) ^ (std::hash<cpp2::u64>()(k) << 3); }
+[[nodiscard]] auto mystruct::hash() const& -> size_t{
+
+size_t ret {0}; 
+ret ^= base::hash() + (ret << 6) + (ret >> 2);
+ret ^= std::hash<cpp2::i32>()(i) + (ret << 6) + (ret >> 2);
+ret ^= std::hash<std::string>()(j) + (ret << 6) + (ret >> 2);
+ret ^= std::hash<cpp2::u64>()(k) + (ret << 6) + (ret >> 2);
+return ret; 
+}
 #line 12 "pure2-hashable.cpp2"
 auto main() -> int{
     mystruct x {2, "three", 4u}; 

regression-tests/test-results/version

@@ -1,5 +1,5 @@
 
-cppfront compiler v0.7.4   Build 9930:1028
+cppfront compiler v0.7.4   Build 9930:1349
 Copyright(c) Herb Sutter   All rights reserved
 
 SPDX-License-Identifier: CC-BY-NC-ND-4.0

source/build.info

@@ -1 +1 @@
-"9930:1028"
+"9930:1349"